<?php
//echo用来输出一个或多个表达式的值
echo "Hello ",123,555.55,true,false,'Over',"\n";
//print_r()来显示数组
$a=[123,'456'];
echo $a,"\n";
print_r($a); // howw are you?
//var_dump()显示一个或多个表达式的类型与值
var_dump($a, false);